1. Field of the Invention
The present invention relates to a circulating apparatus for a linear guideway which usually provides linear-motion transmission for precision control equipments and is widely used on mechanical arms, industrial mechanism, automatic equipments, measuring devices and electronic instruments.
2. Description of the Prior Arts
The working principle of a linear guideway is that a plurality of rolling elements are employed to move between the sliding block and the rail so as to cause relative motion between the sliding block and the rail, and a circulating apparatus is used to make the rolling elements move endlessly.
For example, JP Patent No. 2002-54633 discloses a rolling-element circulating system which is made up of a plurality of independent components, wherein the rolling-element retainers 11, 12, 13, the circulating path 14 and the circulating unit (including 15a and 15b) are independent components. The respective independent components are not integral with the slide block 4, the disadvantage of this circulating system is that it is made up too many independent components, and thus the assembly is complicated and time-consuming. Besides, two many connections between the respective components will adversely affect the stable motion of the rolling elements, and as a result, noise will be caused.
Another rolling element circulating system as disclosed by U.S. Pat. No. 4,662,763 generally consists of two-part split tube of opposed J shape, this design allows the unloading area of the circulating portion of the rolling elements to be a unitary structure, thus eliminating the connection problem. However, the sliding block must be particularly designed to cooperate with the J-shaped tube and the J-shaped tube should be additionally provided with positioning boards, thus complicating the assembly work. Furthermore, there is no space in the J-shaped tube for allowing the flow of the lubrication, the rolling elements cannot be lubricated easily. Besides, due to the J-shaped tube is split into two half parts along the horizontal direction thereof, when the rolling elements move into the J-shaped tube from the loading path, the J-shaped tube is likely to be split apart since the striking force of the rolling element acting on the J-shaped tube is in the direction nearly orthogonal to the dividing line (along which the two parts of the tube are connected) of the tube.
Another rolling element circulating system as disclosed by JP Patent No. 3349238 generally consists of four U-shaped tubes having ball-retaining recess, and the connecting line of (along which the two parts of the tube are connected) the tube is located towards the ball-retaining recess, the defect of this design is that the striking force of the rolling element is applied in the direction orthogonal to the dividing line (along which the two parts of the tube are connected) of the tube, so that the circulating system is also likely to be split apart, and the rolling motion of the rolling elements will be affected adversely.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.